1. Field of the Invention
The present invention relates to a test fixture for electrically connecting an in-circuit tester (print-wiring board tester) and a loaded board.
2. Description of the Related Art
Heretofore, as a fixture used for a tester, such as an in-circuit tester, a probe pin and a spring are combined to form a spring probe pin.
Referring to FIG. 10, the conventional fixture 41 is constituted by having spring probe pins 42, sleeves 43, a top plate 44, a base 45, a support stage 46 and springs 47. The spring probe pins 42 are electrically connected to the sleeves 43. Also, the sleeves 43 are respectively connected through wirings 48 to a tester 49.
In this conventional fixture 41, a loaded board 11 is arranged on the support stage 46. Then, relative to the loaded board 11, a force is applied from the upper surface of the loaded board 11 in the arrow direction (downward). The springs 47 arranged under the support stage 46 are compressed, and the loaded board 11 is pressed relative to the top plate 44. In a short time, connection terminals 13 of the loaded board 11 contact the spring probe pins 42, and the fixture 41 and the loaded board 11 are electrically connected. At this time, the spring probe pins 42 absorb a pressing force from the loaded board 11 by compressing its spring inside the sleeves 43.
Alternatively, referring to FIG. 11, this conventional fixture 51 includes spring probe pins 52, sleeves 53, a top plate 54, a base 55, a support stage 56, springs 57 and an air hole 59 as an air gateway. The springs 57 support the loaded board 11 and the support stage 56. The spring probe pins 52 are electrically connected to the sleeves 53. Moreover, the sleeves 53 are connected through the wirings 58 to the tester 60. Furthermore, to the air hole 59, a suction pump 61 for evacuating air inside the fixture 51 is connected.
In this conventional fixture 51, the loaded board 11 is arranged on the support stage 56. When the loaded board 11 is arranged on the support stage 56, a closed space, which is surrounded by the sleeves 53, the top plate 54, the base 55 and the loaded board 11, is made on the upper surface of the fixture 51. Then, by the suction pump 61, the air in the closed space is evacuated through the air hole 59. As the suction pump 61 evacuates the air in the closed space made on the upper surface of the fixture 51, the closed space gradually falls into a vacuum state. As the closed space falls into a vacuum state, the springs 57 are compressed, and the loaded board 11 is drawn to the top plate 54. The connection terminals 13 of the loaded board 11 contact the spring probe pins 53 as shown in FIG. 12. The loaded board 11 and the fixture 51 are electrically connected.
In the above-described conventional fixture 41, since a pressure is directly applied to the loaded board 11, it has been greatly feared that the loaded board 11 may suffer damage.
Moreover, the conventional fixture 51 has drawn the loaded board 11 to the top plate 54 by making the closed space made between the fixture 51 and the loaded board 11 vacuum. However, attraction by vacuum is directly applied to the loaded board 11, hence it has also been feared that the loaded board 11 may suffer damage.
Furthermore, in general, the loaded board 11 has some warp due to heat at the time of mounting devices 12, or the connection terminals 13 of the loaded board 11 are uneven due to manufacturing variation. However, as the spring probe pins 52, the ones having a constant stroke are used. For this reason, in order to secure the connection between the connection terminals 13 and the spring probe pins 52, the loaded board 11 has been required to be pressed to the spring probe pins 52 so as to absorb the warp of the loaded board 11 or the unevenness of the connection terminals 13.
Accordingly, a force more than necessary is applied to the loaded board 11 depending on the connection terminals 13 of the loaded board 11, as well as it is connected to the spring probe pins 52, hence the connection terminals 13 receive a excessive load from the spring probe pins 42 or 52. As such, in the conventional fixtures 41 and 51, a force more than necessary is applied to the loaded board 11 depending on the connection terminals 13 of the loaded board 11. As a result, it has been feared that the warp of the loaded board 11 may occur.
Heretofore, such warp occurred due to the load of the spring probe pins 42 or 52 has been able to be neglected to some extent. However, in such a case like a bear chip loaded board before resin sealing, which has been used in recent years, since bear chip connection terminals are damaged due to the warp of the board, such warp are not being able to be neglected.
The object of the present invention, in consideration of the foregoing problems, when a test fixture is connected electrically to a loaded board, to provide a test fixture capable of performing secure electrical connection without using spring probe pins or applying an excessive load to connection terminals of the loaded board.
In order to solve the foregoing subjects, a test fixture of the present invention includes a plurality of sleeves, and a plurality of probe pins, each is arranged slidable within a corresponding sleeve and making electrical contact with the sleeve; and an air source connected to the plurality of sleeves, wherein the probe pins are slidable by an air pressure from the air source to electrically connect to connection terminals of a loaded board positioned on the test fixture.
Moreover, the test fixture further includes a base with supports for the loaded board and a top plate in which the sleeves are arranged, wherein the probe pins are slidable by an air pressure generated by injecting air into a space, which is formed by the base, the top plate, the sleeves and the probe pins.